1. Field of the Invention
This invention relates to a solid-state element device comprising a solid-state element sealed by a glass material and, in particular, to a solid-state element device that can prevent the separation of its electrode due to a thermal stress, and can offer good light extraction efficiency and excellent freedom in forming the electrode.
2. Description of the Related Art
Conventionally, a light emitting device is known in which a light emitting diode element (herein called “LED element”) is flip chip-mounted on a substrate or a lead.
Recently, the light emitting device using the LED element as a light source is excellent in environment compatibility and safety, and therefore, its demand has increased. Especially, a high-brightness and large-output type light emitting device is desired as a substitute for use of a white illumination. However, since the heat generation of the LED element increases as the output increases, the emission efficiency lowers to limit the improvement of brightness.
In order to prevent a reduction in reliability due to the heat generation of the LED element, JP-A-2003-218403 discloses a composite light emitting element that an Au bump electrode disposed on the LED element has a size of 30% or more the plane cross section area of the LED element and the LED element is mounted on a submount element.
The composite light emitting element disclosed in JP-A-2003-218403 can improve the heat radiation property by increasing the area of the bump electrode to the plane cross section area of the LED element, so that the brightness can be enhanced according to its increased current.
However, the composite light emitting element disclosed in JP-A-2003-218403 has the problem that, since the Au bump electrode has the increased area and it has a larger thermal expansion coefficient than the LED element or contact electrode, the separation of the LED element may occur when conducting a high-temperature processing such as glass sealing. Thus, the reliability must lower. Further, since current distribution to its light emitting layer is thereby rendered nonuniform, its emission pattern cannot be uniformed. Further, since light emitted from the LED element can be reflected on the bump electrode or submount element, its metal reflection absorption loss will increase to limit the improvement of light extraction efficiency. Further, since the separation occurs at a portion with a large current density, its fed current must be reduced.